Is there a “weekend effect” in adenoma detection rate?A single-center retrospective study

BACKGROUND: The "weekend effect"-inferior patient outcomes on weekends-has been reported across healthcare. Its impact on colonoscopy quality, particularly the adenoma detection rate (ADR), a key predictor of colorectal cancer risk, has not been fully established. This study investigated whether a weekend effect exists for ADR in a large cohort and analyzed potential contributing factors. METHODS: This single-center retrospective study included consecutive patients undergoing colonoscopy from January 2022 to December 2023. Patients were categorized into Weekend (Saturday/Sunday) and Weekday (Monday-Friday) groups. The primary outcome was ADR (proportion with ≥1 adenoma). Data on demographics, withdrawal time, Boston Bowel Preparation Scale (BBPS), and endoscopist experience (Junior <5 years, Senior ≥5 years) were collected. Multivariable logistic regression identified factors independently associated with adenoma detection. Stratified analyses by patient subgroups, withdrawal time, and individual endoscopists were performed. RESULTS: Of 16,550 colonoscopies (4,435 Weekend, 12,115 Weekday), ADR was significantly lower on weekends (24.1% vs. 26.2%, p = 0.006). Median withdrawal time was shorter on weekends (3.61 vs. 4.59 minutes, p < 0.001). After adjustment for confounders, weekend procedures were independently associated with lower ADR (aOR 0.892, 95% CI: 0.821-0.970, p = 0.007), indicating decreased odds of adenoma detection. Other independent predictors included female sex (aOR 0.613, p < 0.001), increasing patient age (aOR 1.050/year, p < 0.001), adequate bowel preparation (BBPS ≥6; aOR 1.407, p < 0.001), and procedure by a senior endoscopist (aOR 1.164, p < 0.001). Subgroup analyses revealed that the weekend effect was significant in specific patient groups compared to their weekday counterparts: females (aOR 0.868, p = 0.022), patients aged 50-59 years (aOR 0.698, p < 0.001), and those with inadequate preparation (BBPS<6; aOR 0.640, p = 0.010). The lower weekend ADR was primarily attributed to two junior endoscopists, with no significant effect observed among senior endoscopists. CONCLUSIONS: A significant weekend effect on ADR was confirmed, principally mediated by shorter withdrawal times and concentrated among junior endoscopists. The effect disproportionately affected women, middle-aged patients, and those with poor bowel preparation. Quality improvement efforts should therefore prioritize enforcing guideline-adherent withdrawal times, optimizing bowel preparation, and providing targeted support to less-experienced endoscopists during weekend services to standardize colonoscopy quality across all days of the week.